Resonance break-off seal



G. K. MEDICUS RESONANCE BREAK-OFF SEAL Filed Jan. 25, 1951 INVENTOR. 605 M v- 1:. Mucus imd States Patent Ofilcc 2,889,067, Patented June 2, 1959 RESONANCE BREAK-OFF SEAL Gustav K. Medicus, Dayton, Ohio Application January 23, 1957, Serial No. 635,923 7 Claims. cram-2.2

(Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without the payment to me of any royalty thereon.

This invention pertains to a break-off seal and more particularly to a break-01f seal within an envelope and inclusive of means and method for rupturing the seal.

The object of the invention is to provide a new and improved break-off seal having particular advantages and which is applicable for general use or as an addition to an associated structure.

In the manufacture of evacuated tubes or the like it may be desirable to release a getter or other substance within the evacuated envelope of the tube after the envelope is sealed. In one established previous device the getter is positioned within a capsule provided with a frangible thin glass tip. An iron ball is also positioned within the envelope or tube. The getter is released within the tube envelope by impacting the ball against it to break the frangible capsule tip. The iron ball and the frangible tip device has objectionable limitations in that it can not be handled for purposes of inspection, assembly with other pieces of equipment, installation and shipment without the exercise of particular care to prevent the iron ball from striking the frangible capsule tip prior to the time that result should properly be achieved. These limitations of the existing type of device are overcome by the device which is contemplated hereby. The present device may be shipped in tubes in completely assembled state without the danger attendant upon the presence of an iron ball within the envelope. During the manufacture of the device which is contemplated hereby the inspecting, handling, shipping and processing of the equipment is accomplished without the exercise of unusual care.

The present invention provides a break-off seal which during its manufacture may be inspected, handled, and assembled where desired with other pieces of equipment, or otherwise processed, with considerable less danger of violating the seal than with any comparable device which has been available on the market previously.

An illustrative embodiment of the present invention is shown in the single figure of the accompanying drawing of a longitudinal sectional view of the device.

In the accompanying drawing the device which is contemplated hereby comprises an outer tube 1 which encloses the seal and which may be attached by the glass blowers art to be continuous with a second tube 2 with which the seal is to be used. The wall of the tube 1 has sealed thereto the outer periphery of a base 3 which serves as a partition between the seal and such other structure as the seal may be attached to. In the illustrative drawing the base 3 serves to separate the interiors of the tubes 1 and 2 into two separate compartments.

The base 3 preferably is substantially of a circular section and during its forming operation the base 3 is drawn upwardly to a constricted portion 4 of thin wall section which preferably serves as the frangible portion of the assembly. The structure continues upwardly through connector 5 and a capsule 6 to a resonance-tuning rod 7 at the terminal end of the seal. The capsule 6 encloses an electromagnetic material represented by a ferromagnetic material 8. The glass connector 5 portion of the device is of such length and structure as to provide a moment arm ofdesired length and mechanical advantage between the ferromagnetic material 8 and the thin wall section 4. The thin wall section 4 preferably is somewhat more constricted than the adjacent wall to thereby concentrate torsion forces applied to the member and initiate its fracture where such fracture is intended. The resonancetuning rod 7 is made of adjustable length and mass during the forming operation of the seal.

The ferromagnetic material 8 preferably is of relatively small mass and provides at its electromagnetic resonant period the force which accomplishes the rupture of the break-off seal which is contemplated hereby. The ferromagnetic material 8 preferably is of a shape elongated axially of the assembly to further concentrate the bending action of the break-01f seal assembly at its constricted portion 4. The ferromagnetic material 8 preferably is advantageously sealed to the break-off glass tip in order to provide a connection which is free of any mechanical damping action. In addition to iron, which generally can not be sealed to glass directly, the ferromagnetic material 8 preferably is selected from a class of glass sealing alloys which do seal directly to glass. Suitable glass sealing alloys illustratively are alloys of nickel with iron, chromium with iron, and the like. The whole piece of ferromagnetic material 8 may be enclosed in glass when preferred, so that no metal surface is exposed to the interiors of either compartments of the tubes 1 and 2. If desired the ferromagnetic material 8 may be completely enclosed within its own sealed glass envelope before it is assembled within the break-01f tip capsule 6 of the assembly.

The fracture of the break-off tip at the constricted portion 4 preferably is accomplished in either of two ways; either by tuning alone or by first tuning to a preferred frequency and then by increasing the intensity of the excitation.

A suitable means for accomplishing the breaking of the seal at the constriction 4 is provided by an electromagnet 10, which preferably is of the horseshoe type in the interest of maintaining a satisfactory magnetic field around the ferromagnetic material 8. The electromagnet 10 preferably is excited by a potential applied to its winding 11. The exciting potential illustratively is a variable frequency adapted to be tuned to or near the mechanical resonance frequency of the elastic system consisting of the ferromagnetic material 8 within the glass capsule 6 and inclusive of the glass rod 5 and the resonance-tuning rod 7, by means of which resonance-tuning rod 7 the assembly is tuned. With this arrangement the oscillating system need not be tuned to any specific frequency for the satisfactory operation of the device. The tuning may be accomplished by the power supply, not shown, which energizes the winding 11 of the electromagnet: 10.

As an alternative, a convenient and readily available 120 cycles per second alternating power sources and a frequency controlling circuit, neither of which are shown, may be used to feed a 60 cycle input to the winding 11 of the electromagnet 10, which corresponds to exciting the ferromagnetic material 8 to 120 cycles per second. Using this alternative method the rupture of the constriction 4 is accomplished by gradually increasing the current which is maintained on the winding 11 of the electromagnet 10.

The oscillation system may be tuned before the assembly of the parts shown in the drawing by the adjustment of the length or the mass of the resonance-tuning rod 7 by the addition of glass to, or the removal of glass from,

the end of the resonance-tuning rod at the time the seal in made. The resonance frequency of the resulting resonant system may in this way be made to approach a desired frequency such as the 120 cycles per second mentioned above, so that the seal constricted portion 4 breaks properly when a suitable exciting force is applied.

It may be shown experimentally that the resonance system may be tuned within of double the frequency that excites the winding 11 of the electromagnet The damping and the resonance frequency of the resonant system may be influenced to an appreciable degree by the insertion of materials of different damping qualities, such as the piece of material between the glass tube 1 and the electromagnet 10. The damping material 15 may be made of rubber, paper, lead or the like.

The completely assembled apparatus may also be regarded as an oscillation system and when so considered its oscillating frequency may be damped by the clamping of additional material 16 to the glass tube 1, the material 16 being rubber, paper, lead or the like.

Representative advantages characterizing the present invention are: (1) that during the process of its manufacture the break-ofi seal itself, mounted in the tube 1, may be handled, tested, packaged, shipped and installed or attached to apparatus with which it is to be used, without the exercise of objectionably special care; (2) that the seal within the tube 1, at the time of its manufacture may, if desired, be sealed directly to a vacuum system or the like, represented by the tube 2 in the drawing, without the exercise of any special care in the handling, testing, packaging, shipping and installation of the equipment; (3) that the perfection of the break-off seal is not endangered by any normal handling where its assembly with other equipment is made subsequently to its shipment; and (4) both the glass and the electromagnetic material in the break-off tip may be of suitably small mass, particularly in comparison with previously available iron balls and break-off tips, such that the handling of the apparatus after the tip has been broken off and is in free motion within the apparatus, is without damage to the remainder of the contents of the apparatus. In connection with this last advantage, the break-off of the small mass of the ferromagnetic material 8 and the glass with which it is associated, occurs at the instant when the oscillation has maximum deviation, thereby imparting minimum kinetic energy to the mass, which function occasions no damage to any adjacent part of the apparatus with which the seal may come into contact.

It is to be understood that the physical structure and the operative reasoning upon which the physical structure is based, may be modified for comparable results and particular advantages attendant thereto, without departing from the scope of the present invention.

What I claim is:

l. A resonance break-off seal comprising a tube, a base secured to and within the tube, a ferromagnetic material supported by the base through a frangible structure attached to the base, and a tuning modifying means attached to and extending as a resonance tuning rod beyond the ferromagnetic material supporting frangible structure remote from the base.

2. The seal defined in the above claim 1, inclusive of a thin glass wall section at the frangible structure and adjacent to the base.

3. The seal defined in the above claim 1 inclusive of a glass connector interposed between the ferromagnetic material and the base for magnifying motion of the ferromagnetic material at the frangible structure.

4. The seal defined in the above claim 1 wherein the ferromagnetic material is completely enclosed within glass.

5. The seal defined in the above claim 1 inclusive of a continuous glass structure extending from the base to beyond the ferromagnetic material as a functional tuning modifying means and being of a length concentrating torque at a predetermined frangible structural part of the break-ofi seal when subjected to suificient oscillatory physical motion.

6. A break-off seal within an envelope comprising an envelope having a wall portion, a base secured to the wall portion and within the envelope, a ferromagnetic material within the envelope, a capsule enclosing the ferromagnetic material, a connector having a proximal end attached through a constricted portion to the base and having a distal end supporting the capsule, and a resonance tuning rod extending away from the capsule at its end remote from the connector for concentrating torque at the constricted portion of the connector on subjecting the ferromagnetic material to oscillatory motion.

7. The break-off seal defined by the above claim 6 in combination with an electromagnet positioned to maintain an electromagnetic field around the ferromagnetic material and the electromagnet being spaced from the envelope wall portion, and a resonance frequency influencing damping material contacting the envelope wall portion which is part of the oscillating system.

References Cited in the file of this patent UNITED STATES PATENTS 2,184,152 Safiir Dec. 19, 1939 

